Perimeter



F. W. JOBE PERIME'IER Nov. 19,

Filed Dec. 31, 1938 FIG! FREDERICK w, JOBE Patented Nov. 19, 1940 Frederick W. Jolie, Rochester, N. Y., assignor to Bausch &.Lomb Optical Company, Rochester, N. Y., a corporation of New York Application December-31, 193 8, Serial No. 248,825

4 Claims.

The present invention relates to ophthalmic instruments and more particularly to instruments for. obtaining color fields, such as perimeters. 1

.One of the objects of the present invention is to provide a new and improved perimeter in which a test stimulus is 'substitutedfor a preexposure field. Another object is to provide a perimeter in which the 'teststimulus 'is presented without distracting the patients attention. A further object is to provide anew and improved target for a perimeter. Still another object is'to provide a perimeter with *a' target by' which the test stimulus can 'be presented by meansof mechanism out of' the patients 'view; These and other objects and advantages*r'eside in certain novel features of construction, arrangement and combination of parts as will hereinafter be more fully set forth and pointed out in the appended claims.

Referring to the drawing:

Fig.l is a perspective view of a perimeter embodying my invention.

Fig. 2 is a rear elevation of my improved targe r I Fig. 3 is a-section taken on line 33-of Fig. '2

Fig.4 is a section taken on line 4 -4 of Fig. 2.

Fig. 5 is a front elevation of the target,

Fig.6 is a fragmentary view of the target strip.- v

My invention may be applied" to a perimeter such -as that shown in Fig. lwherein 'lfldesignatesa base upon oneend of which is mounted an uprightcolumn' H. The perimeter arc I2 is journalled in the'fcolumn H for rotation about a horizontal axis and a bracket l3 fixed to the are l2 carries a light source M for uniformly illuminating the inside or concave face of the are [2. "A counterweight I5 balances the light source l4 and bracket 13 permitting free rotation of the arc I2. A chin rest I6 is fixed on the other end of the base H] to support the head-of the patient in'proper relation to the are l 2. One suitable perimeter to which the present invention may be applied is that described and claimed in Reissue Patent No. 17,987, reissued March 3, 1931, to C. E. Ferree et a1. I

According to my invention, the arc l2 of the perimeter is provided with a track I! on its outside or convex surface. A carriage I8 is provided with upper and lower flanges l9 and 20, respectively, which extend over the track. I]. Two blocks -2l of suitable material such as fiber are secured at the ends-of the upper fiange-l9 -by screws 22 and these blocks 2| each have a; groove 23 for engaging the top edge of the track ll. .Two similar blocks 24 are mounted on pins25ffwhich are slidable in holes at each end of the flange'2fl. These blocks 24 eachhave a groove 26 for engaging the lower edge of the track H. A leaf spring 21 is secured to the bottom of the flange 20 by screws 28 and the ends of this spring press up against the pins 25 and cause the blocks 24 to bear against the edge of the track ll. This frictional contact serves to hold the carriage l8 in any selected position on the track I! regardless of the angular position of the arc I2.'

A bracket 30 secured to or formed integrally with the carriage l8 projects forwardly over the are [2 and a plate 31 is secured at the outer end of this bracket 30'by screws 32. The plate 31 extends down in front of, the arc l2 and is preferably painted the same'color as the inside" or concave surface of the arc I2; 'I prefer to" have both the arc l2 and the plate 3| painted a neutral gray. The plate 31 is formed with an' aperture 33 at which thetest stimulus is presented in a manner to be'presently described.

The bracket-3i] isprovided with a bore 34 and a shaft 35 is journalled in this bore so that its axis is'substantially perpendicular to the plate 3|. Adjacent the plate 3i. the bracket 30 has a slot or recess 36 to accommodate a guide 31 secured on the end' of the shaft 35 by a screw 38. A thin fiat strip39 is slidably mounted in the guide 31 and extends down behind the plate 3! past the aperture33.

A plate 40' is secured at the lower end of the strip 39 facing the 'plate 3| by screws 4|. This plate 40 is painted substantially the same gray as the plate 3I and'arc l2i serieso-f'holes 42, 43, 44, 46 and 41- are formed in-the plate 40- along one edge and these holes; outline the test stimuli. For example. the holes 42 43 and 44 may be of such size as to subtend visual angles of 0.17, 0.5'and 1.0". A piece of whitepa'per 48 may be secured between the plate 40 and strip 4| to constitute the stimulus. fThe three holes 45, 46 and 41 may be all of'such size as to subtend a visual angle of 1.O. The actual stimuli consists of three pieces of paper 49, and 5| secured between thep-late 40 and strip 39 behind the holes 45, 46 and 41, respectively. These papers 49', 50 and 5| are of different colors, for ex-. ample, paper 49 may be green, 50 red and.5| blue. Preferably they are all of the same brightness as the gray but at least the'red'and blue should be of this brightness.

The rear surface of the plate 3| is marked with indicia 52 corresponding to these stimuli and, when the, strip 39 is moved in the guide 31 until its top is at a particular index, the corresponding stimulus is alongside but out of alignment with the aperture 33 of the plate 3|. For example, when the strip 39 is in the position shown in Fig. 2, the hole 45 backed by'the greenipaper 49 is alongside the aperture 33. The backof; the strip 39 .isprovided with a series of depressions 53 corresponding in number and: spacing -.to the stimuli. A spring click 54 carried by the guide 31 engages in these depressions 53 and holds the strip 39 in a selected position. The top of the strip 39 is bent out as indicated at 55 to form a convenient handle for raising or lowering the strip.

A lever 56 is fixed to the outer end of the shaft 35 by a pin 5'1. One arm of the lever 56 extends down adjacent the carriage l8 and carries a pin 58. A handwheel 59, rotatably journalled on a sleeve 59 which is threaded'into the carriage I8, is provided with radial slot 6| into which the pin 58 projects. Thus, turning the handwheel 59 actuates the lever 56 to rock the shaft 35. The other arm of the lever 56 is bifurcated to receive a stud 62 secured on the bracket and two adjustable screws 53 and 64 extend through the bifurcations of this arm to engage, respectively, the top and bottom of the stud 62. These screws 53 and 64 thus limit the rocking of the shaft 35. In order to provide further friction between the carriage i8 and the track H, a friction plug is slidably mounted in the sleeve 63 and urged against the rear of the track H by a spring 65. The tension on this spring 66 may be varied by 'a screw 61 threaded in the outer end of the sleeve 69.

'In operation, the patient is properly positioned at the perimeter with his chin on the chin rest if; and directed to look'at a fixation mark, not shown, in the center of the arc I2. The handwheel 59 is turned clockwise until the strip 39 occupies the position shown in Fig. 2, that is, until the gray portion of the plate closes the aperture 33 in the plate 3|. This gray area provides a preexposure field. The operator moves the carriage 18 around the arc l2 on the track I! and a counter clockwise turn of the handwheel 59 rocks the shaft 35 and strip 39 to move the selected test stimulus into position behind the aperture 33 in the plate 3|. The upper screw 63 has been already adjusted to stop the shaft 35 when the stimulus is positioned concentric with the aperture 33. This position of the strip 39 is shown in dotted lines in Fig. 2.

During the test, the operators hand is out of sight behind the are [2 and there is no visible motion to distract the patient and lead to anomalous results. The operator thus has a choice of different test stimuli which may be instantly substituted at the aperture 33 from a point outside of the patients field of view.

From the foregoing, it will be apparent that I am able to attain the objects of my invention and provide a new and improved perimeter and target. The actual sizes and colors of the test stimuli may, of course, be changed and the sizes, colors, and order recited in the specification are given merely by way of example. Various other modifications can also be made without departing from the spirit of my invention or the scope of the appended claims.

I claim:

1. A target for a perimeter having an are, said target comprising a carriage adapted to be movably mounted on said arc, a bracket on said carriage, a plate secured on said bracket and adapted to face a patient, said plate being neutral gray and having an aperture therethrough, a shaft rotatably journalled in said bracket with its axis perpendicular to said plate, a guide fixed on one end of said shaft adjacent said plate, a strip slidably mounted in said guide, said strip being neutral gray of the same brightness as said plate, a plurality of different test objects spaced longitudinally on said strip and positioned normally out of alignment with the aperture in the plate, means for moving said strip longitudinally to select a particular test object, and means for tilting said strip on said shaft to position the selected test object into alignment with said aperture.

2. A target for a perimeter having an arc, said target comprising a carriage adapted to be movably mounted on said arc, a bracket on said carriage, a plate secured on said bracket and extending down in front of said arc, said plate being neutral gray and having an aperture therethrough, a shaft journalled in said bracket with its axis perpendicular to said plate, a guide fixed on the end of said shaft adjacent said plate, a strip slidably mounted in said guide, said strip being neutral gray of the same brightness as said plate and projecting downwardly behind said aperture, a plurality of test objects positioned along one side of said strip, means for sliding said strip to position a particular test object alongside of said aperture, a lever secured on the other end of said shaft, and means for actuating said lever to rock the strip and move the particular test object into position behind said aperture.

3. A target for a perimeter having an arc, said target comprising a carriage adapted to be movably mounted on said arc, a bracket on said carriage, a plate secured on said bracket and extending down in front of said arc, said plate being neutral gray and having an aperture therethrough, a shaft journalled in said bracket with its axis perpendicular to said plate, a guide fixed on the end of said shaft adjacent said plate, a strip-slidably mounted in said guide, said strip being neutral gray of the same brightness as said plate and projecting downwardly behind said aperture, a plurality of test objects positioned along one side of said strip, means for sliding said strip to-position a particular test object alongside of said aperture, a lever secured on the other end of said shaft, a hand wheel rotatably mounted on the rear of the carriage, means operatively interconnecting the handwheel and the lever whereby movement of said hand wheel actuates said lever to rock the strip and move the particular test object into position in said aperture and means for stopping said strip whenthe test object is centered in the aperture.

4. The combination with a perimeter having an arc and a track on the outside of the arc of a carriage movably mounted on said track, a

bracket secured on said carriage and extending over said arc, a platecarried by said bracket facing the inside of said arc, said plate having an aperture therethrough, a shaft journalled in said bracket with its axis erpendicular to said plate, a guide secured on said shaft adjacent said plate, a strip slidably mounted in said guide, said strip extending downward past the aperture in said plate, a plurality of different test objects positioned along one side of said strip out of alignment with said aperture, means for'sliding said strip in said guide to bring a selected test object alongside of said aperture, means for indicating which test object is alongside the aperture, .and means for tilting the strip on the shaft to position the test object behind said aperture.

FREDERICK W. JOBE. 

